Transfer guards have been used to provide a smooth transition to support objects traveling across a gap between two conveyor surfaces, such as two pulleys of separate belts, and to prevent objects from falling into the gap. One known transfer guard was formed from a single sheet of UHMW (ultra high molecular weight) polyethylene material with a rectangular cross section having beveled edges that is rigidly attached to a bar support that is welded or fastened to the side of the conveyor structure and positioned in the gap. Because the length and width of a gap will vary depending on the width of the conveyor belt and the conveyor system configuration, the above described transfer guard generally had to be custom fabricated on site to ensure proper dimensions. In addition, because a single sheet of polyethylene material is used, if one portion of the sheet is damaged, the whole sheet must be replaced. In addition, because the guard is rigidly attached to the conveyor system, if an object becomes stuck between the guard and the conveyor system, there is no way to release the guard to prevent damage to the conveyor system.
Another known transfer guard takes the form of a transfer plate using one or more roller bars or wheels arranged in one or more successive laterally arranged rows. These systems require a rigid support structure at the sides or underneath the transfer plate to be mounted in the proper location. Such known roller systems are not configured break away or otherwise absorb impacts from objects or belt splices.
One problem resides in the tolerance provided between the above-described transfer guard and the adjacent moving belt surface, which can allow small debris to become lodged between the transfer guard and the belt surface causing damage to the belt as the moving belt surface continuously rubs against the trapped debris. To address this problem, break-away transfer devices are known. With the above-described device, lag bolts were utilized to releasably mount a bar transfer guard to the support plate members or stringers of the conveyor frame structure of the conveyor system. The lag bolts would shear under sufficient force so the transfer guard bar would break away to avoid belt damage.
One drawback of the above-described break-away transfer guard and other transfer devices, such as the device disclosed in U.S. Patent Application Publication No. 2007/0023257 to Schiesser, is the manner in which the devices are mounted to break away during conveyor operations. Transfer devices that have their break-away mountings at the side support plate members or stringers of the conveyor system require that the longitudinally directed forces on the transfer device be redirected and transmitted through the device laterally to the remote break-away mountings. One drawback with these break-away transfer guards is that in the event that the transfer guard breaks away, the transfer guard completely loses functionality requiring replacement of the entire transfer guard.
In one transfer device disclosed in U.S. Pat. No. 3,548,996 to Ellis, a complex series of narrow relief plates are individually removably attached by magnets to corresponding individual slidable mounting blocks having shafts that allow longitudinal movement in the direction of belt travel. The mounting blocks are mounted to a dead plate conveyor, which is stationary and relies upon vibration to move articles, such as glassware. Accordingly, the transfer device disclosed in Ellis appears to be limited to applications where a moving conveying surface is adjacent to a stationary conveying surface having sufficient support structure to which the transfer device may be fixedly mounted.
A transfer guard system comprised of multiple members positioned side-by-side and releasably attached to a support bar for spanning a gap between conveyor systems is disclosed in U.S. Pat. No. 8,365,899 to McKee. Each member is sized to span the entire longitudinal distance of the gap between the adjacent conveying surfaces in the product travel direction and include a pair of depending legs that are releasably mounted to a support bar. Because each member is sized to longitudinally span the entire gap, and gap sizes may vary considerably, different sized members must be made for each gap having a different size.
Another problem encountered in some conveyor applications is that the distance between conveying surfaces in the downstream, longitudinal direction is relatively small. It may be difficult to both position a transfer plate in the gap and secure the transfer plate to the frame of the conveyor or other structures due to the close proximity of the conveying surfaces.